Samsung Galaxy S5 Neo....My calls were working fine until this evening, and now I can only hear or speak to someone if I am using speakerphone, headphones or Bluetooth. The sound is also cutting out when typing. Even speakerphone is cutting out.
While in a call, try adjusting the call volume level and see if that fixes the problem. If that doesn't work, try restarting the S5 Neo by holding the power button for two seconds and selecting the restart icon. Wait for the phone to reboot and make another test call. Let us know if these solutions work or not.